The traditional detailed model of the dual active bridge(DAB)power electronic transformer is characterized by the high dimensionality of its nodal admittance matrix and the need for a small simulation step size,which ...The traditional detailed model of the dual active bridge(DAB)power electronic transformer is characterized by the high dimensionality of its nodal admittance matrix and the need for a small simulation step size,which limits the speed of electromagnetic transient(EMT)simulations.To overcome these limitations,a novel EMT equivalent model based on a generalized branch-cutting method is proposed to improve the simulation efficiency of the DAB model.The DAB topology is first decomposed into two subnetworks through branch-cutting and node-tearing methods without the introduction of a one-time-step delay.Sub-sequently,the internal nodes of each sub-network are eliminated through network simplification,and the equivalent circuit for the port cascade module is derived.The model is then validated through simulations across various operating conditions.The results demonstrate that the model avoids the loss of accuracy associated with one-time-step delay,the relative error across different conditions remains below 1%,and the simulation acceleration ratios improve as the number of modules increases.展开更多
The dual active bridge(DAB)converter is gaining more and more attention in various applications such as energy storage systems,electric vehicles and smart grids.To improve the quality of the input current,a LC filter ...The dual active bridge(DAB)converter is gaining more and more attention in various applications such as energy storage systems,electric vehicles and smart grids.To improve the quality of the input current,a LC filter is often cascaded at the input side of the DAB converter.However,there are instable problems of this cascaded system due to the impedance interactions of the DAB converter and the LC filter,although the DAB converter is stable at the individual operation mode.To assess the stability of the cascaded system of the DAB converter and the LC filter,the impedance model of the DAB converter is firstly developed based on generalized state-space averaging method.The developed impedance model can be used to accurately predict the stability of the DAB converter with its LC input filter.Based on the stability analysis,the optimum filter parameter design guideline is determined.The impedance model and stability analysis are validated by the simulation and experimental results.展开更多
In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on out...In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (C<sub>o,tr</sub>) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low C<sub>o,tr</sub> operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.展开更多
Over the last few years, smart grids have become a topic of intensive research, development and deployment across the world. This is due to the fact that, through the smart grid, stable and reliable power systems can ...Over the last few years, smart grids have become a topic of intensive research, development and deployment across the world. This is due to the fact that, through the smart grid, stable and reliable power systems can be achieved. This paper presents a fuzzy logic control for dual active bridge series resonant converters for DC smart grid application. The DC smart grid consists of wind turbine and photovoltaic generators, controllable and DC loads, and power converters. The proposed control method has been applied to the controllable load＇s and the grid side＇s dual active bridge series resonant converters for attaining control of the power system. It has been used for management of controllable load＇s state of charge, DC feeder＇s voltage stability during the loads and power variations from wind energy and photovoltaic generation and power flow management between the grid side and the DC smart grid. The effectiveness of the proposed DC smart grid operation has been verified by simulation results obtained by using MATLAB and PLECS cards.展开更多
To solve the problem of circulating power of dual active bridge(DAB)DC-DC converter over a wide voltage conversion ratio,this paper proposes a novel synchronous PWM(S-PWM)modulation.Existence of circulating power incr...To solve the problem of circulating power of dual active bridge(DAB)DC-DC converter over a wide voltage conversion ratio,this paper proposes a novel synchronous PWM(S-PWM)modulation.Existence of circulating power increases current stress of devices and decreases efficiency,especially under light load conditions.Several modulation methods have been proposed to overcome the problem.They can reduce or eliminate either input or output side circulating power.In contrast,S-PWM not only eliminates both sides circulating power and reduces current stress,but also achieves zero-current-switching(ZCS)turn-on for all switches and ZCS turn-off for most across the full power range.No auxiliary or snubber circuits are increased.In addition,the control can be simplified so the transmitted power is related to only one variable.The S-PWM has four cases under different gain and power conditions.The detailed operation principle and modes of DAB under S-PWM are analyzed in the paper.In addition,four modulations in literature are discussed,and corresponding comparative analyses with S-PWM are given.Finally,a laboratory prototype is built to verify advantages and effectiveness of the proposed modulation.展开更多
Electrifying the on-board subsystems of aircraft becomes an inevitable process as being faced with the environmental pollution,along with the proposed concept called more electric aircraft(MEA).With the increasing num...Electrifying the on-board subsystems of aircraft becomes an inevitable process as being faced with the environmental pollution,along with the proposed concept called more electric aircraft(MEA).With the increasing number of on-board power electronic based devices,the distribution system of the aircraft can be regarded as an onboard microgrid.As it is known that the load power electronic converters can exhibit constant power load(CPL)characteristics and reduce the system stability,it is necessary to accurately predict and enhance the system stability in designing process.This paper firstly analyzes the stability of an on-board DC microgrid with the presence of CPL.Then,discusses the reasons behind instability and proposes a control strategy to enhance system stability.Finally,the simulation results are worked out to validate the analysis and the effect of the proposed control strategy.展开更多
A series of novel bridged-neonicotinoid analogues were designed and synthesized, which were constructed by starting material 8 with cyclopentenone or cyclohexenone in the presence of catalyst aluminium chloride. All o...A series of novel bridged-neonicotinoid analogues were designed and synthesized, which were constructed by starting material 8 with cyclopentenone or cyclohexenone in the presence of catalyst aluminium chloride. All of the compounds were characterized and confirmed by^1H NMR,^（13）C NMR, HRMS and IR. The bioassay tests showed that compounds 5 and 6a showed higher bioactivities than imidacloprid against Aphis craccivora.展开更多
The dual active bridge(DAB)is a widely used DC-DC topology owing to its ease of control and ability to achieve various control objectives.When designing a DAB-based system under broadband perturbations,one must model ...The dual active bridge(DAB)is a widely used DC-DC topology owing to its ease of control and ability to achieve various control objectives.When designing a DAB-based system under broadband perturbations,one must model the DAB,calculate its input impedance,and analyze the system stability.In this study,two continuous-time impedance models of the DAB,i.e.,a reduced-order model named the power-based impedance model(PBIM)and a full-order model named the generalized state-space average impedance model(GSSAM),are proposed and used to calculate the input impedance in a single-phase modulation mode.The modeling errors are analyzed,the participation factors and residuals are calculated,and a Bode diagram is constructed to illustrate the change in the input impedance with increasing leakage inductance.Simulations are conducted using various circuit parameters to verify the results.The results show that the PBIM exhibits simplicity and accuracy in the low-frequency domain,whereas the GSSAM performs better in the high-frequency domain.展开更多
Energy losses during the conversion and supply of electric power are considered a significant issue and cannot be estimated.Improvement in the efficiency of energy conversion systems is highly restricted because of th...Energy losses during the conversion and supply of electric power are considered a significant issue and cannot be estimated.Improvement in the efficiency of energy conversion systems is highly restricted because of their internal nonlinearity and complexity.Thus,inspired by the successful utilization of robotic chemists,we demonstrate a pioneering concept of artificial intelligence(AI)-aided automatic online real-time optimization of a power electronics converter using a dual active bridge(DAB)converter as an example.An optimal modulation strategy was obtained through repeated automatic exploration experiments on a practical DAB converter platform.Specifically,the DAB experimental platform operated autonomously around the clock for approximately 71 h.It performed 120,000 consecutive experiments(12,000 episodes)within a six-variable experimental space driven by a deep deterministic policy gradient(DDPG)algorithm.The proposed AI-aided automatic online real-time optimization method achieved significantly improved efficiency of power conversion and supply.Consequently,zero carbon emissions may be obtained in the future.展开更多
This paper proposes a system identification framework based on eigensystem realization to accurately model power electronic converters.The proposed framework affords an energy-based optimal reduction method to precise...This paper proposes a system identification framework based on eigensystem realization to accurately model power electronic converters.The proposed framework affords an energy-based optimal reduction method to precisely identify the dynamics of power electronic converters from simulated or actual raw data measured at the converter’s ports.This method does not require any prior knowledge of the topology or internal parameters of the converter to derive the system modal information.The accuracy and feasibility of the proposed method are exhaustively evaluated via simulations and practical tests on a software-simulated and hardware-implemented dual active bridge(DAB)converter under steady-state and transient conditions.After various comparisons with the Fourier series-based generalized average model,switching model,and experimental measurements,the proposed method attains a root mean square error(RMSE)of less than 1%with respect to the actual raw data.Moreover,the computational effort is reduced to 1/8.6 of the Fourier series-based model.展开更多
Solid-state transformers(SSTs)have been widely used in many areas owing to their advantages of high-frequency isolation and high power density.However,high-frequency switching causes severe electromagnetic interferenc...Solid-state transformers(SSTs)have been widely used in many areas owing to their advantages of high-frequency isolation and high power density.However,high-frequency switching causes severe electromagnetic interference(EMI)problems.Particularly,the common-mode(CM)EMI caused by the switching of the dual active bridge(DAB)converter is conducted through the parasitic capacitances in the high-frequency transformer and impacts the system reliability.With the understanding of the CM EMI model in SSTs,CM EMI mitigation methods have been studied.For passive mitigation,the coupled inductor can be integrated with the phase-shift inductor function to reduce CM EMI.For active mitigation,variations in the DAB switching frequency can help reduce the CM EMI peak.An active EMI filter can also be designed to sample and compensate for CM EMI.Using these methods,CM EMI can be reduced in SSTs.展开更多
基金The Technology Project of State Grid Corporation of China Headquarters(No.5400-202318547A-3-2-ZN).
文摘The traditional detailed model of the dual active bridge(DAB)power electronic transformer is characterized by the high dimensionality of its nodal admittance matrix and the need for a small simulation step size,which limits the speed of electromagnetic transient(EMT)simulations.To overcome these limitations,a novel EMT equivalent model based on a generalized branch-cutting method is proposed to improve the simulation efficiency of the DAB model.The DAB topology is first decomposed into two subnetworks through branch-cutting and node-tearing methods without the introduction of a one-time-step delay.Sub-sequently,the internal nodes of each sub-network are eliminated through network simplification,and the equivalent circuit for the port cascade module is derived.The model is then validated through simulations across various operating conditions.The results demonstrate that the model avoids the loss of accuracy associated with one-time-step delay,the relative error across different conditions remains below 1%,and the simulation acceleration ratios improve as the number of modules increases.
文摘The dual active bridge(DAB)converter is gaining more and more attention in various applications such as energy storage systems,electric vehicles and smart grids.To improve the quality of the input current,a LC filter is often cascaded at the input side of the DAB converter.However,there are instable problems of this cascaded system due to the impedance interactions of the DAB converter and the LC filter,although the DAB converter is stable at the individual operation mode.To assess the stability of the cascaded system of the DAB converter and the LC filter,the impedance model of the DAB converter is firstly developed based on generalized state-space averaging method.The developed impedance model can be used to accurately predict the stability of the DAB converter with its LC input filter.Based on the stability analysis,the optimum filter parameter design guideline is determined.The impedance model and stability analysis are validated by the simulation and experimental results.
文摘In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (C<sub>o,tr</sub>) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low C<sub>o,tr</sub> operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.
文摘Over the last few years, smart grids have become a topic of intensive research, development and deployment across the world. This is due to the fact that, through the smart grid, stable and reliable power systems can be achieved. This paper presents a fuzzy logic control for dual active bridge series resonant converters for DC smart grid application. The DC smart grid consists of wind turbine and photovoltaic generators, controllable and DC loads, and power converters. The proposed control method has been applied to the controllable load＇s and the grid side＇s dual active bridge series resonant converters for attaining control of the power system. It has been used for management of controllable load＇s state of charge, DC feeder＇s voltage stability during the loads and power variations from wind energy and photovoltaic generation and power flow management between the grid side and the DC smart grid. The effectiveness of the proposed DC smart grid operation has been verified by simulation results obtained by using MATLAB and PLECS cards.
文摘To solve the problem of circulating power of dual active bridge(DAB)DC-DC converter over a wide voltage conversion ratio,this paper proposes a novel synchronous PWM(S-PWM)modulation.Existence of circulating power increases current stress of devices and decreases efficiency,especially under light load conditions.Several modulation methods have been proposed to overcome the problem.They can reduce or eliminate either input or output side circulating power.In contrast,S-PWM not only eliminates both sides circulating power and reduces current stress,but also achieves zero-current-switching(ZCS)turn-on for all switches and ZCS turn-off for most across the full power range.No auxiliary or snubber circuits are increased.In addition,the control can be simplified so the transmitted power is related to only one variable.The S-PWM has four cases under different gain and power conditions.The detailed operation principle and modes of DAB under S-PWM are analyzed in the paper.In addition,four modulations in literature are discussed,and corresponding comparative analyses with S-PWM are given.Finally,a laboratory prototype is built to verify advantages and effectiveness of the proposed modulation.
基金supported by Ministry of Science&Technology under National Key R&D Program of China(No.2021YFE0108600)Ningbo Science and Technology Bureau under S&T Innovation 2025 Major Special Program(No.2019B10071)Key International Cooperation of National Natural Science Foundation of China(No.51920105011)。
文摘Electrifying the on-board subsystems of aircraft becomes an inevitable process as being faced with the environmental pollution,along with the proposed concept called more electric aircraft(MEA).With the increasing number of on-board power electronic based devices,the distribution system of the aircraft can be regarded as an onboard microgrid.As it is known that the load power electronic converters can exhibit constant power load(CPL)characteristics and reduce the system stability,it is necessary to accurately predict and enhance the system stability in designing process.This paper firstly analyzes the stability of an on-board DC microgrid with the presence of CPL.Then,discusses the reasons behind instability and proposes a control strategy to enhance system stability.Finally,the simulation results are worked out to validate the analysis and the effect of the proposed control strategy.
基金financial supported by Shandong Provincial Natural Science Foundation (No. ZR2015BL009)The Key Research and Development Program of Shandong Provincial (No. 2016GGX107006)+1 种基金National Natural Science Foundation of China (No. 21501066)the Opening Project of Shanghai Key Laboratory of Chemical Biology
文摘A series of novel bridged-neonicotinoid analogues were designed and synthesized, which were constructed by starting material 8 with cyclopentenone or cyclohexenone in the presence of catalyst aluminium chloride. All of the compounds were characterized and confirmed by^1H NMR,^（13）C NMR, HRMS and IR. The bioassay tests showed that compounds 5 and 6a showed higher bioactivities than imidacloprid against Aphis craccivora.
基金Supported by the National Natural Science Foundation of China(52005436).
文摘The dual active bridge(DAB)is a widely used DC-DC topology owing to its ease of control and ability to achieve various control objectives.When designing a DAB-based system under broadband perturbations,one must model the DAB,calculate its input impedance,and analyze the system stability.In this study,two continuous-time impedance models of the DAB,i.e.,a reduced-order model named the power-based impedance model(PBIM)and a full-order model named the generalized state-space average impedance model(GSSAM),are proposed and used to calculate the input impedance in a single-phase modulation mode.The modeling errors are analyzed,the participation factors and residuals are calculated,and a Bode diagram is constructed to illustrate the change in the input impedance with increasing leakage inductance.Simulations are conducted using various circuit parameters to verify the results.The results show that the PBIM exhibits simplicity and accuracy in the low-frequency domain,whereas the GSSAM performs better in the high-frequency domain.
基金support from the National Natural Science Foundation of China(52277083).
文摘Energy losses during the conversion and supply of electric power are considered a significant issue and cannot be estimated.Improvement in the efficiency of energy conversion systems is highly restricted because of their internal nonlinearity and complexity.Thus,inspired by the successful utilization of robotic chemists,we demonstrate a pioneering concept of artificial intelligence(AI)-aided automatic online real-time optimization of a power electronics converter using a dual active bridge(DAB)converter as an example.An optimal modulation strategy was obtained through repeated automatic exploration experiments on a practical DAB converter platform.Specifically,the DAB experimental platform operated autonomously around the clock for approximately 71 h.It performed 120,000 consecutive experiments(12,000 episodes)within a six-variable experimental space driven by a deep deterministic policy gradient(DDPG)algorithm.The proposed AI-aided automatic online real-time optimization method achieved significantly improved efficiency of power conversion and supply.Consequently,zero carbon emissions may be obtained in the future.
基金supported by the Project Support Program for Research and Technological Innovation of UNAM(DGAPA,PAPIIT-2021)(No.TA101421)the strategic project PE-A-04 of CEMIE-Redes。
文摘This paper proposes a system identification framework based on eigensystem realization to accurately model power electronic converters.The proposed framework affords an energy-based optimal reduction method to precisely identify the dynamics of power electronic converters from simulated or actual raw data measured at the converter’s ports.This method does not require any prior knowledge of the topology or internal parameters of the converter to derive the system modal information.The accuracy and feasibility of the proposed method are exhaustively evaluated via simulations and practical tests on a software-simulated and hardware-implemented dual active bridge(DAB)converter under steady-state and transient conditions.After various comparisons with the Fourier series-based generalized average model,switching model,and experimental measurements,the proposed method attains a root mean square error(RMSE)of less than 1%with respect to the actual raw data.Moreover,the computational effort is reduced to 1/8.6 of the Fourier series-based model.
文摘Solid-state transformers(SSTs)have been widely used in many areas owing to their advantages of high-frequency isolation and high power density.However,high-frequency switching causes severe electromagnetic interference(EMI)problems.Particularly,the common-mode(CM)EMI caused by the switching of the dual active bridge(DAB)converter is conducted through the parasitic capacitances in the high-frequency transformer and impacts the system reliability.With the understanding of the CM EMI model in SSTs,CM EMI mitigation methods have been studied.For passive mitigation,the coupled inductor can be integrated with the phase-shift inductor function to reduce CM EMI.For active mitigation,variations in the DAB switching frequency can help reduce the CM EMI peak.An active EMI filter can also be designed to sample and compensate for CM EMI.Using these methods,CM EMI can be reduced in SSTs.
